The present invention relates to a driving circuit of a direct current brushless motor.
FIG. 1 is a block diagram showing a driving circuit of a conventional direct current brushless motor. As shown in FIG. 1, the driving circuit of the conventional direct current brushless motor is provided with sensing parts S1, S2, S3, . . . , and SN arranged around a rotor for generating sensing signals Qs1, Qs2, Qs3, . . . , and QsN according to a position of the rotor, a phase controller 11 for controlling phases of the sensing signal Qs1, Qs2, Qs3, . . . , QsN, stator coil controllers 121, 122, 123, . . . , and 12N for controlling current passing through a stator coil according to output signals Qs11, Qs12, Qs21, Qs22, Qs31, Qs32, . . . , QsN1, and QsN2 of the phase controller 11 and a voltage regulator RE for controlling DC source voltage Vs and supplying predetermined voltage Vc to the sensing parts S1, S2, S3, . . . , Sn and the phase controller 11.
Referring to FIG. 1, rated voltage of the sensing parts S1, S2, S3, . . . , SN and the phase controller 11 is lower than that of the stator coil controllers 121, 122, 123, . . . , and 12N. Accordingly, a resistor R1 for voltage drop is connected to an input terminal of the voltage regulator RE. That is, input voltage of the voltage regulator RE can be obtained by subtracting dropped voltage I.cndot.R1 from the DC source voltage Vs, where I is current passing through the resistor R1. Current I.sub.1 flowing from the voltage regulator RE toward ground is for supplying the predetermined voltage (Vc). Also, total current I.sub.2 of the sensing parts S1, S2, S3, . . . , SN can be obtained by summing current I.sub.21, I.sub.22, I.sub.23, . . . , and I.sub.2N passing through a first sensor S1, a second sensor S2, a third sensor S3, . . . , an Nth sensor SN.
FIG. 2 is a timing diagram for illustrating an operation state of the driving circuit of FIG. 1.
Referring to FIG. 2, QsN denotes a sensing signal from the Nth sensor SN of FIG. 1, QsN1 and QsN2 denote signals from the phase controller 11 of FIG. 1 input into an Nth phase stator coil controller 12N of FIG. 1, and V.quadrature.N denotes voltage applied to the Nth phase stator coil. As shown in FIG. 2, a pulse width of the sensing signal QsN from an nth sensor SN of FIG. 1 is larger by 2.theta. than a half period .pi.. However, the voltage V.quadrature.N applied to the stator coil should be less by 2.theta. than the half period .pi.. Accordingly, the driving circuit of the conventional direct current brushless motor converts output signals S1, S2, S3, . . . , and SN from each sensor into the two signals Qs11, Qs12, Qs21, Qs22, Qs31, Qs32, . . . , QsN1, and QsN2 which are less by 2.theta. than the half period .pi., using the phase controller 11 of FIG. 1. Accordingly, the voltage V.quadrature.N applied to the stator coil of each phase shows a waveform as shown in FIG. 2, to thereby drive the direct current brushless motor.
FIG. 3 is a circuit diagram of the Nth phase stator coil controller of FIG. 1. As shown in FIG, 3, transistors Q1 and Q2 and power transistors Q4 and Q6 are a NPN type, and power transistors Q3 and Q5 are a PNP type, respectively. Accordingly, when the signal QsN1 received from the phase controller 11 of FIG. 1 is high, the transistor Q1 and the power transistors Q3 and Q6 are turned on, so that current of the source voltage Vs passes toward the ground via the power transistor Q3, the Nth phase stator coil .quadrature.N and the transistor Q6. Also, the signal QsN2 received from the phase controller 11 of FIG. 1 is high, the transistor Q2 and the power transistors Q5 and Q4 are turned on, so that current of the source voltage Vs passes toward the ground via the power transistor Q5, the Nth phase stator coil .quadrature.N and the power transistor Q4. That is, the voltage V.quadrature.N applied to the stator coil of each phase shows a waveform as shown in FIG. 2, to thereby drive the direct current brushless motor.
According to the driving circuit of the conventional direct current brushless motor, since the voltage regulator RE and the phase controller 11 are required, the circuit is complicated and much power is consumed.